1. Field of the Invention
The present invention relates to a gas for fabricating a semiconductor device and a fabrication method using the same, and more particularly, to an etching gas mixture for a transition metal thin film and a method for etching the transition metal thin film using the same.
2. Description of the Related Art
In general, with high integration of semiconductor devices, patterns becomes smaller greatly. Thus, the importance of an etching process directly related to formation of a fine pattern has increased. Also, an etching target has been diversified to improve the characteristics of semiconductor devices, including a transition metal as well as conventional materials such as monosilicon, polysilicon, silicon oxide and aluminum.
Generally, the transition metal thin film is widely used as an electrode material for a capacitor. The transition metal thin film is mainly etched by a reactive ion etching and a low-pressure high-density plasma etching. When etching the transition metal thin film by the reactive ion etching, a product of a chemical reaction between an etching gas and the transition metal thin film, e.g., metal halide, exists in a solid state with a high boiling point, so that a physical etching mainly occurs by collision with accelerated ions. Thus, there is a problem in that an etching by-product, dislodged by the physical ion sputtering, is redeposited on the sidewalls of the pattern. If the etching by-product is redeposited on the sidewalls of the pattern, the profile of the pattern becomes inferior. Thus, when the transition metal thin film is used as an electrode of a capacitor, the electrode may not be totally insulated. Also, the pattern is formed in a trapezoid shape, so that the degree of accuracy of the pattern is decreased. Accordingly, it is impossible to form a fine pattern.
When patterning the transition metal thin film by low -pressure high-density plasma etching, the low pressure gives the effect of lowering the boiling point of a product formed by the reaction of a reaction gas with the transition metal. However, the low-pressure high-density plasma etching method gives only limited improvement of the volatility of an etching product, so that the etching product is still redeposited on the sidewalls of the pattern. Thus, it is impossible to form a fine pattern of a critical dimension or less.